Im design a power supply to work with heating wires and one of the task is to estimate the temperature of the bare wire for a given current or power consumption.
I've tried to measure the temperature with a k type thermocouple but the measurement itself affects quite a lot the temperature of the wire in the contact point so I get a lower temperature value.
I've also made measurements of voltage and current on the wire and I don't expect of that measurements to have significant errors so I actually have a reasonable idea of the variation of resistance value.
Even though the X axes (temperature measurements) are wrong, is it reasonble to use the change in the resistance value to stimate the temperature of the wire by using the temperature coefficient of each wire?
Those are the wires I'm working with
Khantal (most likely) 0.3mm:
This is the variation of resistance measured for the wires, nichrome is 1/3 of the diameter of the other two so it's resistance it's significantly bigger:
And this is a plot of T vs delta_R using the linear model
R_t = R20(1 + alpha*delta_t)
According to this nichrome and kanthal are around 1000 degrees while the ferronickel wire is more close to the 600 degrees
I've also found a table that relates color with temperature
The table is consistent in the with the experimental data in the aspect that nichrome and kanthal wires have reached higher temperatures but it's hard to me to choose or to guess which color does have each wire
I would say:
Ferronikel -> bright cherry -> 790
kanthal -> orange -> 940
Ferronikel -> orange -> 940